A high-efficiency tunable TEM-TE11 mode converter for high-power microwave applications AIP Advances 7, 035012 (2017)

A compact metallic photonic crystal mode converter that converts TEM to TE11 mode for a high power transmission system is presented. Metallic photonic crystal is partially filled along azimuthal direction in the device to divide a single coaxial transmission line into two different partitions with different phase propagation constants for phase-shifting. A three row structure is designed and simulated by commercial software cst microwave studio. Simulation results show that it has high conversion efficiency and the bandwidth is 4.1%. Far-field measurement experiment is carried out and get a typical TE11 mode pattern. The result confirms the validity of the design.

Microwave breakdown phenomenon across dielectric window at the vacuum/dielectric interface limits the transmission of HPM and becomes a bottleneck of HPM technology development. Its avoidance or suppression is a major concern among researchers on HPM sources. Currently, the most effective approach is geometrical modification with the goal of altering the trajectories of electrons. In this paper, periodic rectangular grooves perpendicular to microwave electric field, are applied to improve the threshold of breakdown. To clarify the mechanism, the SEEA simulation model based on dynamic analysis and particle-in-cell (PIC) is built in this paper. The grooves change the electrons trajectories and eventually resonant multipactor condition may no longer be satisfied. The suppression effect is influenced by the grooves and each given width relates to an effective power range for suppression. Dielectric breakdown experiments under HPM of S-band at 2.86 GHz are conducted with the grooved dielectric window. The results of the experiment are consistent with theoretical analysis and simulation.

No abstract

No abstract